and its Influence on Climate. 429 



wards inland. He found a great accumulation of fossil trees, as 

 well as fragments not fossilized lying over the whole extent of 

 the land. " This remarkable phenomenon/' says Captain 

 M'Clure, "opens a vast field for conjecture ; and the imagination 

 becomes bewildered in trying to realize that period of the world's 

 history when the absence of ice and a milder climate allowed 

 forest trees to grow in a region where now the ground-willow 

 and dwarf birch have to struggle for existence"*. Trunks of 

 trees, some of them 3 feet in circumference, have been found in 

 Prince Patrick's Island and Melville Island on the spot in which 

 they grew. This place is perhaps at present the coldest spot in 

 the northern hemisphere. 



It is true that Sir Roderick Murchisonf had at one time stated 

 it to be his opinion that those vast quantities of wood found in 

 arctic regions were drifted to their present positions at a period 

 when those regions were submerged. This opinion is now, I 

 believe, generally abandoned. 



But the most remarkable circumstance, and certainly the most 

 unaccountable of all upon the ordinary theories of change of cli- 

 mate during geological epochs, is the fact that we have not only 

 had a succession of cold and warm periods, but cold and warm 

 periods occurring in the same epoch. For example, during the 

 Permian period we have not only evidence of a cold period when 

 glaciers even in our own island reached to the sea-level J, but we 

 have also evidence, as we have seen, of a warm condition of cli- 

 mate extending during that epoch even to the arctic regions. 

 And during the Upper Miocene period we find a cold climate 

 prevailing and glaciers descending to the sea-level in the latitude 

 of Italy §; while during another part of this period we know 

 that the climate of the northern hemisphere was much warmer 

 than at present, and Greenland free of ice and covered with a 

 rich and luxuriant flora reaching up to perhaps the North Pole. 

 Again, during the Pliocene period we have the well-known gla- 

 cial epoch with the northern hemisphere to considerably low la- 

 titudes enveloped in one general capping of ice. And recent 

 discoveries in arctic regions show that at that very period, or 

 perhaps at a period somewhat later, huge forests flourished in 

 North Greenland and the regions about Melville Island, where 

 at present not a shrub can grow, and where nothing is to be 

 seen but interminable fields of snow and ice. 



How are these extraordinary changes of climate to be ac- 



* Discovery of a North-west Passage, p. 208. 

 t Quart. Journ. Geol. Soc. vol. xi. p. 540. 

 X Ibid. p. 197. 



§ LyelPs ' Principles/ vol. i. p. 207. Memoirs of Royal Academy of 

 Sciences of Turin, second series, vol. xx. 



